Once the magnetic coating has been produced on a flexible base in tape form, information media, for example magnetic tapes, are cut to the width required for use and are wound onto flanged reels or flangeless hubs in a length of up to several thousand meters. For this purpose, the hub is fitted with its central bore onto the drive spindle of a winding machine and the information medium is wound up at high speed and under an appropriately adapted winding pressure. In general, to save on cost and weight, the hubs have between the outer winding area and the inner circumference areas of restricted cross section, radially running reinforcing ribs being provided to increase the stability in this zone where the material is thinner. An example of such a hub is mentioned in DE-U 77 22 919. A stackable hub, on which the tape rolls, stacked one on top of the other, are secured against twisting and consequently against damage, is known from. DE 24 48 853.
During winding of the information media onto said hubs as well as during rewinding, such high tensions in the tape may occur that the winding pressure causes the hub bore to be constricted, as a result of which the hubs can no longer be fitted onto the drive spindle of the winding apparatus or cannot be pulled off it. To counter this problem, it is known to produce the hubs from glass fiber reinforced plastic and, if appropriate, to dispense with the thinning of the material mentioned; in addition, hubs of metal are in use. However, for reasons of weight and cost, these solutions have considerable disadvantages.
To avoid the constriction of the hub bore, the already mentioned Utility Model 77 22 919 discloses a radially running threading slit, which is constricted during winding and thereby takes up the winding stress. U.S. Pat. No. 3,632,053 discloses a flanged reel, the hub of which has the generic properties mentioned at the beginning and on which, in addition, flexible intermediate elements are respectively provided between hub and flange in order to avoid transmitting the compression to the flanges. However, as the description reveals, this known hub also requires glass fiber reinforced polystyrene or metal as the material for the hub. It can also be read in the description of EP 0 375 322 of the same applicant that, in spite of the flexible intermediate elements, the inside diameter of the hub is still compressed. In the latter document, to avoid this compression it is proposed to provide between outer and inner ring a number of obliquely running ribs, which have the consequence of twisting the outer ring against the inner ring. U.S. Pat. No. 4,052,020 discloses a reel for a computer tape, on which the outer winding area of the hub is covered with a flexible surface, in order in this way to absorb the stress occurring during winding.
Setting out from the prior art mentioned above, it is an object of the present invention to provide a hub of the generic type mentioned at the beginning which does not have the disadvantages of the prior art, which is furthermore made of plastic and is to do without reinforcing additives, for example glass fibers or glass beads, because this presents recycling problems. Moreover, it is an object of the present invention that dishing of the tape roll does not occur when a number of hubs bearing rolls of tape, known as pancakes, are stacked one on top of the other, and that such a stack of pancakes does not present any problems during transport and storage.